MXPA98010791A - Process and device for improving the purity of a product in a simulated moving bed - Google Patents

Abstract

El dispositivo comprende al menos una columna 1 llena de una pluralidad de lechos An de un adsorbente separado por un platillo distribuidor Pi de fluido. Cada platillo estádividido en una pluralidad de sectores P10, P11 y cada sector comprende al menos una cámara 13 de distribución de fluido perforada de orificios y un espacio de circulación 8 en la vecindad de los orificios. Las cámaras del platillo están conectadas a una línea de transporte 10 hacia el exterior. La línea de transporte 10 relativa a las cámaras sobre un platillo Pi estáenlazada a otra línea de transporte 20 relativa a las cámaras 23 sobre otro platillo (Pi+1óPi+2) dispuestas en la parte inferior del flujo por una línea de derivación L1,2. Esta contiene medios 14, 15, 16 decontrol y de ajuste del flujo de fluido que circula ahíde tal modo que las cámaras de distribución son barridas por un fluido que tiene sensiblemente la misma composición que aquella del fluido que circula a través del espacio de circulación 8 al nivel de cada una de las cámaras.

Description

PROCEDURE AND DEVICE FOR IMPROVING THE PURITY OF A PRODUCT, IN SIMULATED MOBILE BED.

The invention concerns a device for improving the purity of at least one constituent in a mixture circulating through a solid adsorbent or a solid catalyst as well as the process allowing its operation.

In particular, it concerns a chromatographic separation process of at least one aromatic isomer of 8 carbon atoms, in a simulated kidney bed, of a mixture of xylenes and ethylbenzene containing it, and preferably of paraxylene, visualizing the synthesis of terephthalic acid, a petrochemical intermediary in the manufacture of textiles.

More generally, it concerns the separation of at least one isomer from a mixture of constituents, which contain at least one aryl group on which an alkyl group is coupled.

Finally, it concerns the separation of at least one constituent in a mixture for which any chromatographic separation of adsorption or ion exchange is applied, for example. REF. 29059 Reactors or adsorbers currently used are increasingly bulky to deal with a demand in increasingly larger product under investigation.

On the other hand, the investigated product must reach a purity exceeding 99.5% that is not "a priori" compatible with the volume of the load to be treated and consequently with very large reactor capacities.

The secondary technological plane illustrating the application of a simulated adsorption device to jcurrator current is described in patent US 2 985 589 or US 3 268 605.

This device comprises at least one cylindrical column containing a globally cylindrical solid mass of obviously annular section.

A main fluid introduced by a pump travels through the bed of solid along the central axis of the column, according to a displacement that is desired to qualify as "plug flow" displacement. In other words, the fluid must have a uniform composition and frontal displacement at all points of the section of the column.

A device such as that described in the patents US 3 214 247 and US 4 378 292 incorporated by reference makes it possible to achieve this objective. It generally comprises a plurality of beds of an adsorbent, fed by a plurality of distributor plates, each bed being supported by a top mesh substantially perpendicular to the axis of the reactor, and which allows the displacement of the fluid. Each plate is divided into sectors and each distributor plate segment consists of two non-perforated, flat or sharp deflectors (of variable thickness) arranged on the same horizontal plane, between which there is a fluid circulation space. A lower mesh under the baffles allows the fluid to be evenly distributed in the lower bed of the adsorbent.

At the level of each distribution plate, at least four secondary liquid transport lines (load injection line, desorbent injection line, transfer line for an extract and transfer line for a refinery) comprising a set of gates they are connected to the means of exchange of this set of gates.

The injections and trasegados of these fluids are made between certain beds that define areas and move in a regular time space called period T, the introduction and racking points that delimit the areas of interval between the beds (ck) and (c) + i) in the interval between the beds c < k + u and ctk + 2).

If n is the number of beds, n x T defines the time of the. cycle A recirculation pump recirculates fluid from the low end of the column to the high end of the column.

Secondary fluids (filler or desorbent) are introduced or traned (extract, refined) in or after the circulation space through the intermediary of an insertion or perforation chamber pierced with holes.

Each distributor plate can be divided into sectors. According to the patent US 3 789 989, each sector of the dish, delimited by radial walls, consists of a chamber for introducing or conveying the secondary fluid.

In the case in which the distributor plate of each sector_ does not consist more than of a single chamber, each chamber of a given sector is connected by a conduit to a single line of feed or of racked reconnected to the outside of the column.

According to the patent application EP-A-769316, each secondary fluid is introduced or transferred in the middle of its own introduction or transfer chamber which has a variety of holes in front of the circulation space. The upper and lower walls of these chambers constitute the aforementioned baffles, then, when the distributor plate of each sector consists of several chambers, each chamber of a sector of the bed is connected by a conduit to a line destined to receive a single fluid. either to feed the appropriate chamber the refined or the extract. For example, if each sector consists of four chambers, one dedicated to the load, the second to the desorbent, the third to the refined and the fourth to the extract, the CF chamber of the determined sector that receives the load F will be reconnected to a line that receives all the conduits of different CF chambers related to the same bed of adsorbent.

In a paraxylene separation unit operating in a simulated mobile bed, and consisting of two adsorbers arranged in series of twelve molecular sieve beds each, a deformation (or drag) of the longitudinal concentration profiles has been shown for a lack of results in relation to the ideal results expected.

In particular, the drag of the concentration in impurities at the level of the decanted extract is manifested by a significant decrease in the purity of the extract (less than 99%) in relation to the expected purity (greater than 99.5%).

The analysis of the problem, carried out on the separation unit, has shown that these deformations (or drags) of the longitudinal concentration profiles were due to parasitic circulations through each of the distribution chambers arranged on the sectors of each dish and this during periods when there is no introduction or transfer of the fluid through the related chamber.

It is in particular the exchange of matter, due to turbulence at the level of the orifices of the distribution chambers between the main fluid circulating in the circulation space and the fluid contained in the chambers. This phenomenon is known to generate slight trawls.

It is also, above all, recirculation in a distribution chamber of one sector of the pan to the similar chamber of another sector of the same pan via the interconnection pipe that relates these chambers to each other and the transport line to the outside of the adsorbent.

This recirculation is due to slight pressure differences that exist between the sectors of the same saucer, in theory, this pressure should be the same everywhere on the same saucer. In practice, there are slight differences due to various imperfections such as the imperfections of travel of the main fluid through the adsorbent beds, and this induces, during periods when there is neither introduction nor transfer of the secondary fluid in a chamber. , a recirculation of a part of the main fluid monitored at the level of the circulation space of a sector where the pressure is higher, towards the circulation space of a sector where the pressure is lower and this via the orifices of the related chambers.

The part of the recirculated main fluid enters one of the chambers through the orifices of the related chamber belonging to the higher pressure sector.

This part of the fluid is then directed towards the similar chamber belonging to the lower pressure sector via the interconnection pipe that connects these chambers between them.

Finally, this part of the fluid joins the main fluid in the circulation space of the lower pressure sector when passing through the orifices of the chamber of this sector.

The expense of recirculation between two sectors of the same dish is a function of the differences in pressures between these two sectors, as well as the size of the holes in the chambers of the related sectors.

The residence time of the recirculating fluid from a chamber of one sector to the corresponding chamber of another sector is itself a function of the volume of the start and arrival chambers, the volume of the pipe that connects them and the recirculation expense between the two cameras.

If the saucer consists of multiple sectors there will be a general recirculation combined from the sectors where the pressure is the highest towards the sectors where the pressure is the least high, this recirculation is carried out with a mean global residence time TR.

In this unit operating in simulated mobile bed, the composition of the main fluid at the level of a saucer evolves constantly as a function of time. This is due to the advance of the longitudinal concentration profile that moves under the action of the circulation of the main fluid.

Taking into account the parasitic circulation observed, it turns out that on a plate considered at a given moment, on the one hand, the main fluid having a given composition arrives and on the other hand, the part of the main fluid recirculated from a part of the sectors towards the other sectors of that same dish, which has a composition corresponding to that which the main fluid had a moment before, the time difference being equal to the residence time TR of the recirculated fluid part.

Everything then happens as if a part of the main fluid arrives on each plate with a certain delay equal to the residence time TR.

The mixing of this part of the recirculated fluid with drawback, with respect to the main fluid modifies the overall composition of the combined fluid and then causes a systematic retro-mixing at the level of each pan. This has a deformation, or drag, of the profiles of longitudinal concentration, and is translated by a loss of performance, such as the decrease in the purity of the extract that can reach, for example, up to a point.

To avoid this problem, the suppression of the circulation of the fluids in the chambers by counter-return valves arranged on the access lines to the chambers could be visualized, but this solution is impractical since the fluid in the case of a single chamber it can circulate in one direction or another. In addition, these valves can present maintenance problems that can not be resolved due to their inaccessibility.

The object of the invention is to remedy the drawbacks of the prior art.

Another object is to improve the purity of the product under investigation and particularly in the case of reactors or adsorbers of very large diameter.

More precisely, the invention concerns a method of chromatographic separation of a charge in a simulated mobile bed device comprising a plurality of beds (Ai to An) of a solid or adsorbent, contained in at least one chromatographic column, a distribution plate of fluid between each bed, each distributor dish comprising at least one perforated distribution chamber of orifices and a fluid circulation space in the vicinity of said orifices of the chamber, the said chamber being connected to a transport line extending between the chamber and a point located outside the column, during a period T of the cycle, an injection of the load, a raffinate of a refining, an injection of "desorbent and a racking of the extract into and from a chamber of distribution belonging to different saucers, the procedure that is characterized in that it is permanently circulated at an expense appropriate a volume of circulating fluid in the column in a derivation line that relates the chambers of a distributor plate Pi to the chambers of another distributor plate in the lower part of the fluid displacement Pi + j, distant from at least one bed, during at least one period T of the cycle, the period T corresponding to the time of circulation of the fluid in a bed of solid, the so-called distribution chambers not receiving during the said period nor the charge injection or of desorbent or the raffinate of a raffinate or an extract, the flow of circulating fluid in the branch line and in the chambers are adjusted in such a way that the circulation chambers are swept by a fluid that ostensibly has the same composition as that of the circulating fluid through the circulation space at the level of each of the chambers of the Pi and Pi + j saucers.

The position of the plate located in the lower part, is defined in relation to the direction of the advance of transfer points and introduction from sequences of permutations.

By operating according to the procedure, any stagnation of residual fluid in the distribution chambers is avoided. The distribution chamber from which the fluid (The main fluid called "pump around") is aspirated, until circulating a fluid whose composition is visibly that of the fluid that crosses at the same time the circulation space in the distributor plate that relates an adsorbent bed to another bed of adsorbent.

Also, the circulation chamber in which the fluid is introduced via the derivation line will circulate - a fluid whose composition is substantially that which crosses at the same time the so-called circulation space.

It has been observed under these conditions that a purity was obtained at the level of the investigated product, for example of paraxylene, very interesting (more than 99.8%) and a yield superior to 95%, in a simple way and with suppression of the disturbance affecting the profile of concentrations moving in the adsorbent beds.

It was further observed that it was not very necessary to rinse the stagnant residual fluid before the extracting operation of the extract, as long as the method according to the invention ensures a permanent rinsing of the lines and of the supplementary gates and at the same time avoiding a decrease in productivity in the product under investigation.

According to a characteristic of the method, the chambers of the distributor plates linked by the branch line can be separated by a bed of adsorbent.

In this case, the cost of the fluid circulating in the branch line is usually and appreciably the daily volume available in the related distribution chambers and the branch line between the parts of transport lines between two successive chambers of chambers, divided for the period of the cycle.

It can be verified that this expense is higher than the natural flow of the fluid due to the slight pressure differences (for example, some grams per cm2) that exist between the same chambers of sectors of the same saucer.

According to another characteristic, they can be separated by two beds of adsorbent, the derivation line being connected between the dishes Pi and the dish P1 + 2, in the lower part. In that precise case, the fluid cost is decreased since it takes into account the length of the derivation line and especially the duration of the circulation that corresponds to two periods.

By circulating the fluid between two plates separated from two beds, there is more than one higher load loss that imposes with more certainty the direction of the circulation of the fluid in the branch line.

Means for controlling and adjusting the expense of the fluid circulating in the chambers and the branch line are arranged on it. These can comprise a line calibrated according to the volumes involved for the derivation between two beds and as a function of the circulation time of the fluid to obtain the appropriate expense.

A counter-return valve disposed on this downstream line of the mentioned means prevents any return of liquid upwards.

An all-or-nothing gate, disposed on the branch line can also prevent any circulation of fluid in one direction or the other.

A pump that relates the two chambers and arranged on the aforementioned line upwards of these control or adjustment channels can facilitate the circulation of the fluid in this line.

A tolerance of ± 50% can be accepted around the calculated value of the expense, particularly in the absence of an automatic regulation of the expenditure control, advantageously ± 25% and preferably ± 15%, without the results, ie the purity of the product investigated, expressed in terms of the expense of fluid bypass are substantially affected.

The distributor plate may consist only of a single distribution chamber per sector. According to a first variant of the method, the flow of the circulating fluid in the branch line between the distribution plates (Pi and Pi + i) can be canceled during a period when the related chambers of the distributor plate Pi receive the charge injection or of desorbente or of another fluid ("flush-in" of rinsing) or the raffinate of the refining or of the extract or of another fluid ("flush out").

According to a second variant of the process, during the period of racking of an extract or raffinate, on a given distribution plate not containing a single chamber per sector, the extract or the refining of the plate Pi is transferred, the bypass expense being canceled (for the counter-return valve) and during the following period, the extract or the refining of the Pi + i dish and the Pi dish is transferred, the circulation of fluid in the bypass line having been restored.

During the charge or desorbent injection period, a part of the charge or the desorbent can be introduced into an appropriate plate Pi via the bypass line and during the following period, the entire load is sent to the next distributor plate. I, the derivation expense being canceled (by the counter-return valve).

The distributor plate may consist of two, three or four distribution chambers, advantageously two, since the flow of circulating fluid in all the beds of the same area is kept substantially constant.

In the case in which it contains two, according to a first variant, a first chamber may be intended to receive a racking of the extract or raffinate and a second one intended to receive a loading or desorbent introduction. According to a second variant of a two-chamber distributor plate per sector, a first chamber may be designed to receive a refining rake or a desorbent introduction and a second chamber may be adapted to receive an extract racking or a load introduction. A washing fluid (internal reflux of the investigated product, paraxylene, for example) from the outside can also be introduced into said second chamber.

Outside the periods of extracting raffinate and refining and introducing loading and desorbent on the aforementioned chambers, the fluid of the first chambers of a Pi distributor plate is transferred to introduce, thanks to the bypass line, in the second chambers. Pi + i distributor saucer cameras.

According to the first variant, during the period of extracting the extract or refining, the extract or the refining of the first chambers can be transferred from a Pi plate, the expense of the branch line that feeds the second chambers of the plate is canceled. P? +? and Pi is introduced into the second chambers of the fluid from the first chambers of the Pi-ti cymbal via the branch line.

According to the second variant, during the period of racking of the raffinate, the refining of the first chambers of a Pi dish can be transferred, the expense of the bypass line supplying the second chambers of the Pi + i dish is canceled and introduced into the second chambers of the Pi dish the fluid that comes from the first chambers of the P? + dish? via the derivation line.

During the period of extracting the extract, the extract of the second chambers of the Pi dish can be transferred, the expense of the bypass line supplying the second chambers of the Pi dish is eliminated and inserted into the second chambers of the Pi + 1 dish. the fluid that comes from the first chambers of the Pi dish via the bypass line.

During the period of introduction of the desorbent, the desorbent can be introduced into the first chambers of a Pi dish, the expense of the bypass line feeding the second chambers of the Pi + i dish is eliminated and inserted into the second chambers of the Pi dish. the fluid that comes from the first chambers of the PÍ + I dish via the corresponding derivation line.

During the period of load introduction, the load can be introduced into the second chambers of a Pi dish, the expense of the bypass line feeding the second chambers of the Pi dish is canceled and the fluid of the first chambers of the dish is transferred Pi to enter it thanks to the line of corresponding -derivation in the second chambers of the dish P? + ?.

According to a third variant of a distributor plate with two chambers per sector, a first intended to receive an extract racking, a second one intended to receive a loading or desorbent introduction or a refining racking, outside the periods of extracting the extract and refining and introducing charge and desorbent onto the aforementioned chambers, the fluid from the first chambers of a distributor plate Pi can be transferred to be introduced thanks to the branch line in the second chambers of the Pi + i distributor plate.

During a period of the cycle, the extract of the first chambers of a Pi plate can be transferred, the expenditure of the branch line feeding the second chambers of the Pi + i plate is eliminated and it is introduced into the second chambers of the Pi plate of the fluid from the first chambers of the Pi + i cymbal via the branch line.

During a period of the cycle, the refining of the second chambers of a Pi dish can be delayed, the fluid of the first chambers of the Pi + i dish is eventually clarified via the bypass line between the Pi + i and Pi dishes and is introduced of the fluid coming from the first chambers of the Pi dish in the second chambers of the Pi + i dish via the bypass line between the Pi and P? + dishes? .

If the gate all or nothing on the line of derivation between the saucers P? +? and Pi is closed, the transfer of fluid from the first chambers of Pi + i is canceled.

During a period of the cycle relative to the first and third variants, it can be introduced from the outside of the column of the charge or of the desorbent in the second chambers of a Pi dish, the flow of fluid from the bypass line supplying the pipelines is canceled out. second chambers of the Pi dish, and the first chambers of the Pi dish of the fluid that is introduced to the second chambers of the Pi + x dish via the bypass line are transposed.

When the distributor plate comprises four distribution chambers per sector, a first destined to receive an extract racking, a second destined to receive a refining racking, a third destined to receive a desorbent introduction and a fourth destined to receive an introduction of load, can be transferred the fluid of the first chambers and the second chambers of a distributor plate Pi to introduce it respectively in the third and fourth chambers of the plate P? +? outside the periods of racking of extract or refining and introduction of desorbent or load on said plate Pi.

During a period of the cycle, the extract of the first chambers of a Pi dish can be clarified, the flow of fluid from the bypass line supplying the third chambers of the Pi + i dish, the third and fourth chambers of the dish is canceled Pi respectively receiving the fluid from the first and from the second chambers of the preceding plate Pi + i via the branch line and the second chambers of the plate Pi which receives from the fluid supplying the fourth chambers of the Pi + i plate via the line of corresponding derivation.

During a period of the cycle, the refining of the second chambers of a distributor plate Pi can be delayed, the flow of fluid from the bypass line supplying the fourth chambers of the Pi + i pipe, the third and fourth chambers of the pipe is canceled. Paltillo Pi receiving respectively the fluid of the first and second chambers of the preceding dish P? + ?, via the branch line and the first chambers of the Pi dish, which receives from the fluid that feeds the third chambers of the next dish Pi + i via the corresponding derivation line.

During a period of the cycle, the desorber can be introduced from the outside of the column, into the third chambers of a Pi dish, the fluid is diverted from the bypass line that feeds the third chambers of the Pi dish, the first and second chambers. chambers of the Pi dish, which receives the fluid that feeds respectively the third and fourth chambers of the Pi + i dish via the bypass line and the fourth chambers of the next dish Pi that receives the fluid from the second chambers of the preceding dish Pi + i via the corresponding derivation line.

During a period of the cycle, the load in the fourth chambers of a Pi dish can be introduced from the outside of the column, the flow of fluid from the bypass line supplying the fourth chambers, the first and second chambers of the dish, is canceled Pi distributor that feeds respectively the third and fourth chambers of the following dish Pi + i via the bypass line and the third chambers of the Pi dish that receive the fluid from the first chambers of the Pi + i dish via the bypass line.

The invention also concerns the device for the application of the method. More precisely, it concerns a device for chromatographic separation of a load in a movable bed simulated comprising at least one column filled with a solid or adsorbent, the column comprising a plurality of beds, a distribution plate Pi of fluid between each bed, each distributor plate that is divided into a plurality of sectors of distributor plates, each distributor plate sector comprising at least one perforated distribution chamber with holes and a fluid circulation space in the vicinity of the mentioned holes of the chamber and the chamber mentioned being connected to a transport line extending between the chamber and a point located outside the column, the device being characterized in that the transport line relative to the distribution chambers of a Pi dish is linked by a Bypass line to the transport line relative to the distress chambers distribution of another plate Pi + j arranged downwards (in relation to the direction of advance of the permutations of the transport lines) and in which the branch line consists of means for controlling and adjusting the flow of circulating fluid, thereby that the distribution chambers are swept by a fluid that. it has sensibly the same composition as that of the fluid that circulates through the circulation space at the level of each of the chambers.

The means for controlling and adjusting the fluid expense generally consist of a counter-return valve or other equivalent means.

These means comprise a means for measuring the flow of circulating fluid in the branch line and a regulating gate of the expense, possibly regulated by means of the measurement of the expense.

The branch line may further comprise a pump, generally disposed upstream of the expense measurement means. It may also include an all-or-nothing gate, and prevent any fluid circulation during the periods of injection or racking in or out of the column.

According to a first embodiment of the device, each distributor plate sector can consist of a chamber, the number of beds in the column being even and the number of distributor plates Pn being odd, the branch line (L?, 2) that relates the distribution chambers of the distributor plate Pi to those of the distributor plate P2, the branch line (L3,4) relates the distributor chambers of the distributor plate P3 to those of the distributor plate Pn to the main fluid recirculation line of the latter bed to the first bed.

According to another variant, the number of beds being even, the number of distributor plates Pn being odd, the derivation line relates the recirculation line of the main fluid to the distribution chambers of the distributor plate Pi, the branch line L?, 3 it relates the distribution chambers of the distributor plate P2 to those of the distributor plate P3, and the branch line (Ln - ?, n) relates the distributor chambers of the distributor plate Pn-i to those of the distributor plate Pn.

According to another variant, the number of beds being odd, the number of distributor plates Pn, being even, the branch line (L?, 2) relates the distribution chambers of the distributor plate Pi to those of the distributor plate P2, the line of distribution derivation (L3,4) relates the distributor chambers of the distributor plate P3 to those of the distributor plate P4 and the branch line (Ln - ?, n) relates the distributor chambers of the distributor plate Pn-i to those of the distributor plate Pn .

It may be advantageous if the branch line relates the chambers of a Pi dish to those of a Pi + 2 dish. In that case, the chambers of the Pi plate may be related to those of the plate P2 by the branch line, or the chambers of the plate Pn-i may be related to those of the plate Pn by the branch line.

According to a second advantageous embodiment of the device, each distributor plate sector Pi of the column can comprise two fluid distribution chambers, a first one adapted to receive a first fluid, a second adapted to receive a second fluid and a first line of fluid. derivation that relates the first chambers of a Pi dish to the second chambers of a Pi + i dish and a second derivation line that relates the first chambers of the dish P? +? to the second chambers of the cymbal Pi + 2 and so on.

According to another variant, when the distribution plate Pi comprises by sector two fluid distribution chambers, a first adapted to receive a first fluid and a second adapted to receive a second fluid, a first derivation line can relate the first chambers of a saucer Pi to the first chambers of a Pi + i and a saucer. second derivation line relates the second chambers of the Pi dish to the second chambers of the Pi + i dish.

According to a third embodiment of the device, each distributor plate sector Pi of the column can comprise four fluid distribution chambers, a first adapted to receive a first fluid (extract), a second adapted to receive a second fluid (refined) , a third adapted to receive a third fluid (desorbent) and a fourth adapted to receive a fourth fluid (charge). A first derivation line relates the first chambers of a Pi dish to the third chambers of a Pi + i dish and a second derivation line relates the second chambers of a Pi dish to the fourth chambers of a P? +? Dish.

The invention concerns in the end the use of the device for the separation, in particular, of paraxylene in a mixture of xylenes and ethylbenzene.

The invention will be better understood in view of the figures schematically illustrating preferred embodiments of the device, among which: Figure 1 shows, at the level of a sector, a longitudinal section of an adsorbent column, in a simulated moving bed, in an even number of beds and in an odd number of distributor plates in a single distribution chamber per sector, comprising bypass lines of controlled flow according to the invention.

Figure 2 illustrates two cymbals divided into sectors of cymbals related to each other by the branch line according to the invention.

Figure 3 shows a longitudinal section of a column where each distributor plate contains, according to a radial plane, two distribution chambers.

- Figure 4 represents a longitudinal section of a column where each dish contains four distribution chambers per sector.

According to FIG. 1, a cylindrical chromatographic column 1 containing a plurality of beds An of an adsorbent, of the zeolitic molecular sieve BaX, for example, is shown.

The main fluid is extracted from the lower end of the column by a line 2 to be recycled by a pump 3 and a line 4 at the upper end of this column where it is introduced to the upper bed Ai of adsorbent by the lines .

For the separation of paraxylene from a charge of xylenes, there are generally two columns of twelve beds each, the twenty-four beds are divided into at least four zones, each zone is delimited by an injection of a fluid from the outside of the column (of the desorbent or of the load for example) and a racked-up of another fluid (extract or refined for example). For example five beds are reserved for zone I, nine beds for zone II, seven beds for zone III and three beds for zone IV. Under the bed Ai is located the distributor plate Pi of fluid that must pass through the next bed.

Each distributor plate Pi according to FIG. 2 is divided into sectors of cymbals Pio, Pn, P12, P13, Pi4, P15, delimited by walls 28 which are radial, as indicated on the figure, which are substantially parallel to a diameter of the spine. Each sector contains a distribution chamber Ci of fluid, longitudinally, either for introduction of secondary fluid, or for the clarification of secondary fluid as indicated below and each chamber is connected via a line 29 to a line 140. This line located inside or outside of the column recovers the fluids from all the chambers and is related to a secondary fluid transport line 10.

Each distributor plate Pi is located between two beds of adsorbent. Each sector of the Pio a Pis plate represented schematically in angular form on FIG. 1 contains an upper mesh 6 that supports the upper bed of adsorbent Ai, substantially perpendicular to the axis of the column and which allows the displacement and collection of the bed fluid Ai . It also comprises two non-perforated deflector plates 7 arranged on the same horizontal plane, between which a fluid circulation space 8 is arranged. A lower mesh 9 under the deflectors 7 allows the fluid to be evenly distributed in the lower bed of adsorbent.

At the level of each distributor plate Pi, the secondary fluid transport line 10, 20 connected to at least four secondary fluid transport lines not shown on FIG. 1 (charge injection line, desorbent injection line, line of stripped of an extract and clarification line of a refined one) each comprising a sequential gate, represented symbolically by the gate 11, 21 arranged as close as possible to the branch line. These sequential gates can be replaced by a rotary gate that secures the set of secondary fluid injections in the column or traverse of the fluid of the column, the derivation of one line to the other according to the invention, being able to be performed outside or in the inside of the rotary gate by the incorporation of rotating connections and of appropriate calibrated lines or holes.

The aforementioned gates as a whole are connected to sequential permutation control means adapted to periodically advance each point of secondary fluid injection or secondary fluid transfer of a bed in the direction of the circulation of the main fluid, that is to say of the high towards the low. There is thus a simulated moving bed running countercurrently.

On figure 1, each chamber Ci, (13, 23, 33, 43) of distribution of the secondary fluid contains in its lower part holes 18 advantageously arranged below the circulation space 8, by which the secondary fluid is displaced to be, either introduced into the next bed after being mixed into the main fluid when crossing the main bed, or to be removed by the appropriate transport line.

The distribution chambers 13 of the pipe Pi are connected to the distribution chambers 23 of the distributor plate P2 located between the adsorbent beds A2 and A3, via a bypass line L?, 2. The volume of fluid passing through the chambers 13, the part of the transport line 10 to the bypass line, the bypass line L?, 2, the part of the transport line 20 communicating with the distribution chambers 23 of the Saucer P2 as well as the aforementioned chambers 23 are well known.

Each branch line (L?, 2, L3,4, ...) contains an expense meter, an expense control gate 15 connected to the expense meter and a counter-return valve 16 at the bottom of the flow of fluid adapted to the flow of the fluid from the chambers 13 to the chambers 23. A pump 17 eventually makes it possible to replace the insufficiency of loss of charge between the chambers of two cymbals. An all-or-nothing gate 19 disposed on the branch line can prevent any flow of fluid in the branch line.

The device of a single distributor chamber per distribution plate sector can operate as follows: during the period of extracting an extract by line 10, the gate 11 is opened, the extract is removed by the chambers 13 of the Pi plate , the counter-return valve 16 prevents any circulation of the fluid in the circulation line L?, 2. During the next period, the gate 11 being closed, the decanting of the Pi-i dish extract is removed via the chambers 23 and the Pi dish via the chambers 13, the gate 21 being open and the circulation of the extract in the bypass line having been restored with an expense _ such as that indicated above. The same procedure shall be followed for the removal of the raffinate from the raffinate on the plate Pj and Pj + i during the cycle.

According to another variant, in which the bypass line comprises the gate 19, when the extract is removed by the line 20 and the open gate 21, any transfer of the plate Pj is prevented by the line 10 closing this gate 19.

During the charge injection period during the cycle, a part of the load can be introduced into the pan Pk via the distribution chambers 13 and the load transport line 10 and the other, smaller part in the pan Pk + i via the branch line, the line 20 and the chambers 23, the gate 11 being open and the gate 21 being closed.

During the following period, gate 11 is closed, gate 21 is opened, the entire load is sent to chambers 23 of the distributor dish Pk + i, the expense of the bypass line is canceled by the counter-return valve . It would proceed in the same way for the introduction of desorbent on the dishes Pi and PÍ + I during the cycle.

According to another variant, when the load is introduced on the pan Pk, the damper 19 can be closed on the branch line to prevent any transport of the fluid in the pan Pk + ?.

On the Pi and Pi + dishes? that do not receive any secondary fluid (neither charge or desorbent injection, nor clarified extract or refining), gates 11, 21 on transport lines 10 and 20 being closed and the main fluid coming from bed Ai is combined in the deflectors 7 and the circulation space 8 travels through. A part circulates through the orifices of the chambers 13 of the Pi pan, sweeps the chambers 13, the transport lines 29, the line 140, the transport line 10. , the branch line L?, 2 and reaches under controlled flow through the flow meter 14 and the gate 15 connected to the flow meter the transport line 20 of the fluid. The check valve 16 remains open. The fluid is introduced at the end of a period in the chambers 23 of the pan P? + ?, which are also swept by the fluid which has substantially the same composition as that of the fluid, which, during the period, passed through the A2 bed, circulates in the circulation space 8. The fluid of the chambers 23 is evacuated through the holes 18 in the circulation space 8 where it is mixed with that which crosses the previous bed.

Figure 3 illustrates a Pi sector of a distributor plate Pi containing two fluid distribution chambers 13a, 13b that also have the role of fluid baffles, with the same references for the same media as those of figures 1 and 2. Their holes are made substantially in front (preferably arranged anywhere) at the level of the space 8. The first chambers 13a are adapted to receive a first fluid and the second chambers 13b are adapted to receive a second fluid . The connection lines of all the first chambers 13a of the same distribution plate Pi are related to the transport line 10a of a fluid. This transport line 10a of the plate Pi communicates with the transport line 20a of the plate P2 by the branch line L?, 2 containing the means 14, 15, 16, and possibly 17 and 19 mentioned in Figure 2. The line 20a is connected to all the second chambers 23a of the pan P2.

The first chambers 23b correspond to the sectors of the distributor plate P2 are connected by a branch line L2,3 substantially identical to the line L?, 2 and by a transport line 30b, to the second chambers 33b of the distributor plate P3. During a period of the cycle in which the removal of clarification takes place, for example, the extraction of the extract of the first chambers 23b of the pan P2 is removed, the expense of the branch line feeding the pan P3 is canceled by the check valve and it is introduced into the second chambers 23a of the plate P2 of the fluid coming from the first chambers of the plate Pi, the counter-return valve being open, the gates Ia and 21a being closed.

The raffinate of the raffinate can be carried out under the same conditions.

During the period of the cycle in which the desorbent or charge is introduced, it is introduced from the outside of the column, of the load for example in the second chambers 23a of a pan P2, the gate 21a being open, the valve counter-return being closed in the branch line L?, 2 and the clarification of the first chambers 23b of the plate P2 is removed from the fluid that is introduced into the second chambers 33b of the plate P3 via the branch line L2,3, the gates 21b and 31b being closed.

Outside the points of racking or introduction on the above-mentioned chambers of the column, the fluid of the first chambers of the Pi plate is transferred, the gateway being closed and introduced by the line L?, 2 to controlled flow, in the second chambers of the pan P2, the gate 21a being closed.

The two chambers have been represented in a horizontal plane but they could be arranged in or above the circulation space 8 between the deflector plates 7.

Figure 4 illustrates a fluid distributor plate Pi with four independent chambers 13a, 13b, 13c and 13d per sector also having the role of fluid deflector. The same means of Figures 1 and 2 have the same functions and the same references.

The second chambers 13a are adapted to receive refining. They are related to the gateway through the transfer line 10a.

The fourth chambers 13b below the second ones are adapted to receive the load. The transport line 10b and its gate 11b that feeds it.

The first cameras 13c on the same plane as the second ones are adapted to receive the extract. The transport line 10c and its gate 11c allow the transfer to the outside of the column.

The third chambers 13d below the first ones are adapted to receive the desorbent. The lOd transport line and its lid gate feed it.

The holes 18 of the four chambers 13a, 13b, 13c and 13d are open in the circulation space 8.

At the level of each sector of the pan P2, there are the same chambers 23a, 23b, 23c, and 23d in the same positions as before as well as the organs that are related to them.

The second chambers 13a of the plate Pi are connected to the fourth chambers 23b of the plate P2 via the branch line L2,4 and the first chambers 13c of the plate Pl are connected to the third chambers 23d of the plate P2 via the branch line L? ,3.

Outside the periods of fluid transfer (extract or refining) and fluid introduction (charge, desorbent), the fluid of the first chambers 13c and the second chambers 13a of the Pi plate are clarified to enter respectively the thirds 23d and fourth chambers 23b of the P2 cymbal and so on.

The cameras 13d and the chambers 13b of the plate Pi are fed from the main fluid (line 4) recirculated by the recycling pump 3 (see figure 1), the gates lla, llb, 11c and lid as well as the gates 21a, 21b , 21c and 21d are closed.

During a period of the cycle relative to the extracting of the extract, the extract of the first chambers 23c of the plate P2 is routinely transferred, the expense of the line L?, 3 which supplies the third chambers 33d of the plate P3, the third and fourth chambers of the dish P2 receiving respectively the fluid of the first and second chambers of the Pi dish via the corresponding bypass line.

During a period of the cycle relative to the racking of the raffinate, the refining of the second chambers of a Pi dish is more often delayed, the flow of fluid from the bypass line L2.4 feeding the fourth chambers of the dish P1 + 1 is canceled , the third and fourth chambers of the plate Pi receiving the fluid of the first and second chambers of the preceding plate Pi + i respectively via the corresponding branch line.

During a period of the cycle relative to the introduction of the desorbent, it is introduced from the outside of the column of the desorbent in the third chambers of a Pi dish, the flow of the fluid from the bypass line feeding the third chambers of the Pi dish is canceled, the first and second chambers of the plate Pi receiving the fluid that feeds respectively the third and fourth chambers of the plate Pi + i via the branch line and the fourth chambers of the next plate Pi that receives the fluid from the second chambers of the preceding plate Pi-i via the corresponding derivation line During a period of the cycle relative to the introduction in the column of the load in the fourth chambers of a plate Pi, the fluid expense of the branch line supplying the fourth chambers of the plate Pi, the first and second chambers of the Pi dish that respectively feed the third and fourth chambers of the next dish P? +? via the corresponding branch lines and the third chambers of the plate Pi that receives the fluid from the first chambers of the plate P? -? via the corresponding derivation line.

Example By way of example of embodiment according to the invention, the case of a paraxylene separation unit is described from a charge comprising mainly a mixture of orthoxylene, metaxylene, paraxylene, and ethylbenzene. This unit operates according to the principle of adsorption in a simulated mobile bed and comprises two absorbers with a diameter of 4.8 m. , arranged in series of 12 beds of adsorbent each, for example a faujacita exchanged with barium.

Dispensing plates are arranged between each bed, each sector of the dish containing two distribution chambers, the first chamber that is intended to receive a solvent introduction or a raffinate raffinate, the second chamber that is intended to receive a charge introduction or a sample of the extract (see Fig. 3).

Under normal operating conditions, the pressure drop on a bed between two successive distributor plates is approximately 0.31 Kg / cm2. The period that defines the time of permutation of the injections of racking from one bed to another, and then represents the time of advance of the profiles of concentration from one bed to another, is 84 seconds, knowing that the average cost of circulating fluid through the beds is 800 m3 / h.

In the absence of a device according to the invention, an expenditure of parasitic recirculation of one part of the sectors of one pan to the other sectors of the same pan, of the order of 1 to 3 m3 / h, is estimated on each distribution pan. spending being due to the slight differences ^ of pressure that exist between the sectors of the same dish.

In order to correct this recirculation phenomenon which is detrimental to the results of the process, at each stage, between two successive distributor plates, a branch line according to the invention is arranged, which relates the first chambers of the plate Pi to the second chambers of the plate P ? +? (This is the case of Fig. 4).

For the first bed of each adsorber, the branch line relates the main line 4 to the second chambers of the plate Pi (this is the case of Fig. 4).

For the last bed of each adsorber, the derivation line relates the first chamber of the dish Pn to the main line 2 (this is the case of Fig. 1).

On each of the branch lines there are disposed a device of measurement of expense, a gate of adjustment of expense, a check valve and a gate (19) of opening / closing sequentially, each of these elements being selected to give a slight loss of charge.

The optimal expense in the derivation line between two consecutive cymbals Pi and PÍ + I was determined as follows: - volume of the first distribution chambers and associated pipelines of the Pi: 276 1. - volume of the bypass line: 170 1. - volume of the second distribution chambers and associated pipes of the Pi + dish: 228 1. - volume total to circulate between two successive cymbals: 674 1. - flow displayed in the branch line: 674 1. X 3,600 sec./84 sec. = 28, 886 l./h. or approximately 29 m3 / h.

This expense can be ensured without a pump thanks to the loss of load available between two distributor plates and the slight losses of load of the elements used on the branch line.

In addition, this expense being very much superior to the flux of parasitic recirculation on a saucer, the effects of the parasitic recirculation are canceled out.

It has been shown that thanks to this device according to the invention: - Paraxylene purities greater than 99.9% can be easily obtained, - It is no longer necessary to rinse the lines prior to the transfer of the investigated product, which results in an operation of the mobile bed. in simulated countercurrent in only 4 zones and not in 5 or 6 zones that are necessary according to the prior art.

It is noted that in relation to this date the best method known by the applicant to carry out the aforementioned invention is that which is clear from the present description of the invention.

Having described the invention as above, it is claimed as property in the following,

Claims (40)

1. Method of chromatographic separation of a charge in a movable bed device, simulated, comprising a plurality of beds of a solid or adsorbent contained in at least one chromatographic column, a fluid distributor plate between each bed, each distributor plate that is divided into a plurality of sectors, each distributor plate sector comprises at least one perforated distribution chamber of holes and a fluid circulation space in the vicinity of said chamber orifices, said chamber being connected to a line of transport that extends between the chamber and a point located outside the column, is carried out during a period of the cycle, an injection of the load, a raffinate of a raffinate, an injection of desorbent and a racking of an extract in and from a distribution chamber belonging to different saucers, the procedure that is characterized in that it has been circularly circulating, permanently at an appropriate expense, a volume of circulating fluid in the column in a branch line that relates the chambers of a distributor plate to the chambers of another distributor plate at the end of the flow, distant from at least one bed, during at least one period T of the cycle, the period T corresponding to the time of circulation of the fluid in a bed of adsorbent, the aforementioned distribution chambers not receiving during said period neither the injection of charge or of desorbent nor the racking of a refining or of an extract, the expenditure of fluid circulating in the branch line and in the chambers being adjusted in such a way as to sweep said circulation chambers by a fluid that has substantially the same composition as that of the fluid circulating through the circulation space at the level of each of the chambers of the Pi and Pi + j saucers.

2. A method according to claim 1, characterized in that said distributing chamber chambers are separated by a bed of adsorbent.

3. A method according to claim 1 or 2, characterized in that the fluid expense circulating in the branch line is the quotient of the volume available in the related distribution chambers and the branch line, divided by the period of the cycle, plus or minus 50 % and preferably more or less 15%.

4. Method according to one of claims 1 to 3, characterized in that said distributor plate chambers are separated by two beds of adsorbent.

5. A method according to claim 4, characterized in that the flow of fluid flowing in the branch line is the quotient of the volume available in the distribution chambers and the branch line, divided by twice the period of the cycle, plus or minus 50% and preferably more or less 15%.

6. Method according to one of claims 1 to 5, characterized in that the flow of the fluid circulating in the branch line between the distribution plates Pi and Pi + i when the chambers of the distributor plate Pi receive the injection is canceled over a period. load or desorhente or other fluid ("flush-in") or the raffinate of refining or extract or any other fluid ("flush out").

7. Process according to one of claims 1 to 5, characterized in that, during the period of transfer of an extract or a raffinate, on a given distributor plate containing only one chamber per sector, the extract or refining of the plate Pi is transferred. , the bypass expense being canceled (by the counter-return valve) and during the following period, the extract or refining of the Pi + i and the Px saucer is transferred, restoring the circulation of the fluid in the bypass line.

8. Process according to one of claims 1 to 5 and 7, characterized in that during the charge or desorbent injection period, a part of the charge or the desorbent is introduced into an appropriate plate Pi via the branch line and during the following period , the entire load is sent on the next distributor plate Pi + i, the bypass charge being canceled (by the counter-return valve).

9. Method according to one of claims 1 to 5, characterized in that each sector of the distributor plate comprises two distribution chambers, a first one designed to receive a racking of the extract or raffinate and a second one intended to receive a loading or desorbent introduction and in which, outside the periods of racking the extract and refining and introducing load and desorbent on the mentioned chambers, the fluid is collected from the first chambers of a Pi distributor plate to be introduced, thanks to the bypass line, in the second chambers of the Pi + 1 distributor saucer.

10. Process according to claim 9, characterized in that during a period, the racking of the extract or the refining of the first chambers is collected from a plate Pi, the flow of the branch line that feeds the second chambers of the plate is canceled. ? and is introduced into the second chambers of the Pi dish of the fluid coming from the first chambers of the dish P? +? via the derivation line.

11. Method according to one of claims 1 to 5, characterized in that each distributor plate sector comprises two distribution chambers, a first intended to receive a racking of the extract, a second one intended to receive a loading or desorbent introduction or a raffinate of the raffinate and in which out of the periods of After extracting and refining and introducing charge and desorbent into the aforementioned chambers, the fluid from the first chambers of a distributor plate Pi is transferred to introduce it thanks to the branch line in the second chambers of the distributor plate P? + ?.

12. Process according to claim 11, characterized in that during a period, the extract of the first chambers of a Pi dish is transferred, the expense of the bypass line supplying the second chambers of the Pi + i dish is eliminated and it is introduced into the second chambers. of the Pi plate of the fluid coming from the first chambers of the Pi-i plate via the branch line.

13. Process according to claim 11 or 12, characterized in that during a period, the refining of the second chambers of a plate Pi is transferred, the fluid of the first chambers of the plate Pi-i is transferred via the branch line between the plates P? -? and Pi and the fluid that comes from the first chambers of the Pi dish in the second chambers of the dish I + I is introduced via the branch line between the dishes Pi and P? + ?.

14. Method according to one of claims 9 to 13, characterized in that, during a period of the cycle, the load or the desorber is introduced from the outside of the column into the second chambers of a Pi plate, the flow of the line is canceled bypass that feeds the second chambers of the Pi dish, and the fluid from the bypass line that feeds the second chambers of the Pi dish is transferred from the first chambers of the Pi dish, and the fluid from the first chambers of the Pi dish is transferred from the first chambers of the Pi dish. it is introduced into the second chambers of the Pi + i cymbal via the branch line.

15. Process according to one of claims 1 to 5, characterized in that each sector of the distributor plate comprises two distribution chambers, a first one designed to receive a raffinate raffle or a desorbent introduction and a second one designed to receive a charge introduction, desorbent or a racked extract and in which, outside the periods of transfer of extract and refining and introduction of charge and desorbent on the aforementioned chambers, the fluid of the first chambers of a pi distributor dish is transferred to introduce it, thanks to the branch line, in the second chambers of the distributor plate P? + ?.

16. Process according to claim 15, characterized in that during a period, the refining of the first chambers of a plate Pi is delayed, the expense of the branch line supplying the second chambers of the plate P? +? and it is introduced into the second chambers of the saucer Pi of the fluid that come from the first chambers of the saucer P? -? via the derivation line.

17. Method according to one of claims 15 to 16, characterized in that during a period, the extract of the second chambers of a Pi dish is transferred, the expense of the bypass line supplying the second chambers of the dish P ± is canceled and introduced in the second chambers of the Pi + i dish of the fluid coming from the first chambers of the Pi dish via the bypass line.

18. Method according to one of claims 15 to 17, characterized in that during a period, the desorber is introduced into the first chambers of a Pi dish, the expense of the bypass line supplying the second chambers of the Pi + i dish is canceled and introduced in the second chambers of the saucer Pi of the fluid coming from the first chambers of the saucer P? -? via the corresponding derivation line.

19. Method according to one of claims 15 to 18, characterized in that during a period, the load is introduced into the second chambers of a plate Pi, the expense of the branch line feeding the second chambers of the plate Pi is canceled and the fluid of the first chambers of the Pi dish to enter it thanks to the corresponding branch line in the second chambers of the Pi + i dish.

20. Method according to one of claims 1 to 5, characterized in that each distributor plate sector comprises four distribution chambers, a first intended to receive an extract racking, a second one intended to receive a refining rake, a third destined to receive an introduction of desorbent and a fourth destined to receive an introduction of load and in which the fluid of the first chambers and of the second chambers of a distributor plate Pi are transferred to introduce it respectively in the third and fourth chambers of the Pi + 1 dish outside of the periods of transfer of extract or refining and introduction of desorbent or load on said Pi dish.

21. Method according to one of claims 1 to 5 and 20, characterized in that during a period of the cycle the extract of the first chambers of a Pi dish is transported, the flow of fluid from the bypass line supplying the third chambers of the dish is canceled out. P? + ?, the other chambers receive the fluid according to claim 20.

22. Method according to one of claims 1 to 5 and 20 and 21, characterized in that during a period of the cycle, the refining of the second chambers of a distributor dish P ± is transferred, the fluid consumption of the bypass line supplying the fourth chambers of the Pi + i dish, the other chambers receive the fluid according to claim 20.

23. Method according to one of claims 1 to 5 and 20 to 22, characterized in that during a period of the cycle, the desorber is introduced from the outside of the column into the third chambers of a Pi dish, the expense of the derivation line is canceled which feeds the third chambers of the Pi dish, the other chambers receive the fluid according to claim 20.

24. Method according to one of claims 1 to 5 and 20 to 23 characterized in that during a period of the cycle, the load in the fourth chambers of a Pi plate is introduced from the outside of the column, the flow of fluid from the bypass line supplying the fourth chambers, the other chambers receive the fluid according to claim 20.

25. Apparatus for chromatographic separation of a load in a simulated bed comprising at least one column filled with a solid or adsorbent, the column comprising a plurality of beds, a distribution plate Pi of fluid between each bed, each distributor plate being divided into a plurality of sectors of distributor plates, each sector of distributor plate comprising at least one distribution chamber perforated with holes and a fluid circulation space in the vicinity of said holes of the chamber, the mentioned camera that is connected to a transport line that extends between the camera and a point located on the outside of the column, the device that is characterized in that the transport line relative to the distribution chambers of a cymbal Pi it is linked by a bypass line to the transport line relative to the distribution chambers of another plate Pi + j disposed in the lower part of the stream (in relation to the forward direction of the permutations of the transport lines) and in which the branch line contains the means for controlling and adjusting the flow of circulating fluid, in such a way that the distribution chambers are swept by a fluid that has substantially the same composition as that of the fluid that circulates through the circulation space at the level of each of said cameras.

26. Device according to claim 25, characterized in that the means for controlling and adjusting fluid expenditure contain a counter-return valve.

27. Device according to claim 25 or 26, characterized in that said means for controlling and adjusting the expense comprise a means for measuring expenditure and a regulating gate for expenditure, possibly connected to the means for measuring expenditure.

28. Device according to one of claims 25 to 27, characterized in that the branch line comprises a pump.

29. Device according to one of claims 25 to 28, characterized in that the branch line comprises an all-or-nothing gate.

30. Device according to one of claims 25 to 29, characterized in that the transport lines comprise sequential gates.

31. Device according to one of claims 25 to 29, characterized in that the transport lines are linked to at least one rotating gate and in which the branch line is inside the rotary gate or outside it.

32. Device according to one of claims 25 to 31, characterized in that the number of beds is even, the number of distributor plates Pn is odd, the line "by pass" (L?, 2) links the distribution chambers of the distributor plate Pi to those of the distributor plate P2, the branch line (L3,4) connects the distributor chambers of the distributor plate P3 to that of the distributor plate P4 and the branch line (Ln) connects the distribution chamber of the distributor plate Pn to the recirculation line of the main fluid from the last bed An to the first bed Ai.

33. Device according to one of claims 25 to 31 characterized by the number of beds is even, the number of distributor plates Pn is odd, the branch line links the recirculation line of the main fluid to the distributor chamber of the distributor plate Pi, the line of branch L2,3 connects the distribution chambers of the distributor plate P2 to those of the distributor plate P3, and the branch line (Ln - ?, n) links the distributor chambers of the distributor plate Pn-i to those of the distributor plate Pn .

34. Device according to one of claims 25 to 31, characterized in that the number of beds is odd, the number of distributor plates Pn is even, the branch line (L?, 2) links the distribution chambers of the distributor plate Pi to those of the distributor plate P2, the branch line (L3,4) connects the distribution chambers of the distributor plate P3 to those of the distributor plate P and the branch line (Ln -? N) connects the distributor chambers of the distributor plate Pn-i to those of the distributor plate Pn.

35. Device according to one of claims 25 to 31, characterized in that the branch line connects the chambers of a blade Pi to those of a plate Px + 2.

36. Device according to claim 35, characterized in that the branch line connects the chambers of the plate Pi to those of the plate P2 or the chambers of the plate Pn-i to those of the plate Pn.

37. Device according to one of claims 25 to 31, characterized in that each distributor plate segment Pi comprises two fluid distribution chambers, a first adapted to receive a first fluid, a second adapted to receive a second fluid and in a first line (L 2) bypass links the first chambers of a Pi dish to the second chambers of a P1 + 1 dish and a second bypass line (L2,3) links the first chambers of the P1 + 1 dish to the second chambers of the dish P1 + 2 and so on.

38. Device according to one of claims 25 to 31, characterized in that each distribution plate sector Pi comprises two fluid distribution chambers, a first adapted to receive a first fluid and a second adapted to receive a second fluid in which a first line bypass links the first chambers of a Pi dish to the first chambers of a Pi + i dish and a second bypass line connects the second chambers of the dish Pi to the second chambers of the Pi + i dish.

39. Device according to one of claims 25 to 31, characterized in that the distribution plate sector Pi comprises four fluid distribution chambers, a first adapted to receive a first fluid (extract), a second adapted to receive a second fluid (refined), a third adapted to receive a third fluid (desorbent) and a fourth adapted to receive a fourth fluid (charge) and in which a first derivation line links the first chambers of a Pi dish to the third chambers of a dish P ± + iy a second derivation line links the second chambers of a Pi dish to the fourth chambers of a Pi + i dish.

40. Use of the device according to one of claims 25 to 39 for the separation of at least one aromatic isomer of eight carbon atoms in a mixture of xylenes and ethylbenzene.